Automatic all-relay telephone system



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AU'roMA'r'Io 'ALL-RELAY TELEPHONE SYSTEM John H. Voss, Rochester, N. Y., assignor to Automatic Electric Laboratories, Inc., Chicago, Ill., a corporation of Delaware Application January 8, 1947, Serial No. 720,757 27 claims. (o1. 179-18) This invention relates in general to telephone Systems, but more particularly to automatictelephone systems of the all-relay type, generally similar to those described in Patent 2,491,291 issued to Voss and Jones on December Y13, 1949, and in the co-pe'nding application Serial No. 720,756, led January 8, 1947, now Patent No. 2,535,764, granted December 26, 1950.

Telephone systems of this type, Awhile eomparatively new, are known to be extremely fast in operation, 'and quite reliable in performance. They tend however, to be high in cost, particularly in the larger sizes employing selectors, because of the very large number of relays required. This high cost has been perhaps, the most important handicap encountered in the commercial exploitation of the all-relay system.

The principal method employed in the past to reduce the cost of this type of system has been to remove all control relays from the individual linenders, and concentrate them in control units common to a plurality of linenders, leaving in these latter units only the tens and units relays and one or more connect relays for connecting them to the control equipment as and when re'- quired. More recent developments, including said aforementioned co-pending applications,

teach the use of trunk-selecting equipment cornmon to a plurality of selectors or connectors, rather than making such equipment an integral part of each switch.

The main purpose of the present invention is to continue this process, and still further reduce the cost of such systems, by removing most of the remaining control relays from both the selectors and the connectors, and placing these relays in common control units accessible to a plurality of said switches. Such arrangements are known in connection with Strowger switch systems and other machine switching systems, where however, they have less utility, and, in connection with Strouger systems, at least, tend to reduce somewhat, the inherent flexibility of this equipment.

One feature of my invention is therefore the provision of a, selector from which have been removed, not only the trunk-selecting relays, but also the line, release, hold, counting, and transfer relays, as well as the dial tone, timing, and service restriction features normally included in eachY individual selector switch.

Another feature of my invention is the ,provision of a connector from which have been re'- moved, not only all trunk selecting relays, but alsov the pulse counting and digit transfer relays. and the line testing and ringing control relays,

2 as well as the busy tone and reverting call tone features normally included in each individual connector switch.

Another feature of my invention is the provision of separate common control units for linefinders, selectors and connectors, as well as separate trunk selecting units for both selectors and connectors, and the progressive release of these units for use by other switches, as the call progresses through its different stages.

A further feature of the invention is the forced release of all common control units if held for longer than a certain fixed maximum time interval.

Still another feature of the invention is the momentary busying of the idle connectors of a group when the associated common control unit is seized by one of said connectors.

Another feature of the invention lies in the association of two or more common control units with any given group of selectors, and the use of said control units in rotation. It will be obvious that such an arrangement could also be used with the connectors if desired, with only minor 'changes in the circuits. .e Other objects and features of the invention will be apparent from the specification and claims which follow, considered in conjunction with the associated drawings comprising Figures 1 to 18 inclusive, which show one embodiment of the invention as applied to a1000 line system of the type indicated. It will be understood that the arrangement shown is but one embodiment of the invention, and that various modifcations and re-arrangements are possible, without departing from the scope of the invention. e

With reference to the drawings, Figures 1 to 16, when arranged as indicated in Figure 18, with the adjoining conductors properly aligned, represent a, sufficient amount of the essential parts of the system to enable the operation thereof to be thoroughly understood.

Thus, Figures 1 to 4 inclusive represent the line and linender equipment, and the finder control relays, Figure 1 showing the line equipment, Figure 2 the linender equipment, and Figures 3 and 4 the linender common control and allotter equipment.

3 of the common trunk selecting equipment associated with the selectors.

Figures 11 to 15 inclusive show one of the connectors of the system and the common control equipment associated therewith, Figures 1l and 12 being the connector and Figures 13, 14 and 15 the common control unit.

Figure 16 shows a common group of P. B. X trunk selecting relays associated with the connectors, while Figure 17 presents in somewhatV more detail than the previously mentioned drawings, the manner in which a plurality of control units may be connected to a plurality of selectors.

To describe the equipment comprising the various gures of the drawing in more detail, Figure l shows two three-relay line circuits, consisting of the line relays |20 and |50, cutoff relays ||0 and |40, and lockout relays |00 and |30 respectively. The upper line circuit may be considered f as being connected to a trunk repeater such as the rectangle with a multiple to the corresponding terminals on the tens relays ofl the selectors, while the lower line circuit may be considered as being connected to a subscribers station such as indicated by the circle |10, with a multiple to the corresponding terminals of the tens relays in the connectors. There is nothing new or novel in these circuits.

Figure 2 shows one of the linefinders associated with the stated line circuits. This linefinder is also similar to others used previously with only minor circuit changes, and is shown in skeleton form with only seven relays. Relays 200 and 2 0 represent the tens or group relays, of which a full complement would be ten for each nder,

each relay having line contacts for ten lines. Relays 220 and 230 represent two ol the ve units relays required, each units relay providing access to two line circuits through the contacts of each group relay. Relay 240 is the units switching or sub-group relay which serves to divide each group of ten lines into a high and a low sub-group, namely 1 to 5 and 6 to 0, and to select one of the two lines selected by any operated tens and units relays. Relays 250 and 260 are the connect relays, which operate upon the Yinitiation of a call to connect the finder control and allotter equipment momentarily to this nder-selector link.

Figure 3 shows a portion of the finder control relays, including the tens and units marking relays, ten of each of these being required. Relays 300 and 3|0 represent two of the tens marking relays, which are operated from the line equipment, and serve to turn to operate the tens relays of the finders. sive represent four of the units marking relays, which also operate from the line equipment, through make contacts on the tens marking relays, and serve to control the units relays of the finders. control relays. It is operated from the'connect relays in the finder and serves to prepare the release of the marking relays.

Figure 4, comprising relays 400 to 410 inclusive shows the balance of the nder control unit. Relays 400 and M0 represent two service restriction marking relays having to do with calls to and from trunks. They are operated from the tens marking relays of Figure 3, and their mark- Relays 320 to 350 inclu-V Relay 360 is one of the miscellaneous ing contacts, which are grounded from the units marking relays of Figure 3, are cross connected as required to operate corresponding service restriction relays in the selector contol units to mark certain calls as trunk calls, and to prevent.

certain subscribers from making trunk calls which other subscribers may be privileged to make. Relays 420, 425, 435 and 440 are ca1l passing relays, which function whenever a calling line is not cut through promptly, to disengage the seized link and pass the call to the next idle link. VRelay 430 is an all-trunks-busy relay whichreleases when all links are busy to operate a meter; relay 445 is a reset relay which operates on the seizure of the last link to reset the allotter; and relay 450 is an overow relay which operates upon the initiation of a `call with all links busy to operate an overflow vmeter, and to give a busy tone in case the call is from a trunk. Relays 460 and 410 represent the allotter relays, which preselect the next idle link to be used for a call from any line or trunk in the associated hundreds group. These relays, one of which is required for each link, are normally energized, and release in turn as the corresponding links are taken into use. When the last link is taken into use, the reset relay acts to lreoperate all allotter relays whose associated links are idle, to again preselect the irst idle link.

Figure 5 shows three of the selector miscellaneous relays, relay 500 being the su/itching" relay, which operates from the selector units relays to switch a call through. Relay 5|0 is a busy relay, which may operate from either the comon control equipment or the trunk selecting equipment to give a busy tone to the calling line, and relay 520 is one of the connect relays, which operate from the finder to connect the link momentarily to an idle control unit. Two connect relays are required in each selector for each control unit associated therewith, the companion relay to relay 520 being relay 650 in Figure 6. A second pair of connect relays is represented by the rectangle 508 in Figure 5. For details of the interconnections of these relays, see Figure 17.

vIn Figure 6, the other half of the selector, relay 600 is the units switching relay corresponding to relay 240 in the nder, and is operated from the trunk selecting equipment. Relays 6|0 and 620 are units relays, also operated from the trunk selecting equipment, such as shown in Figures 9 and 10, and relays B30 and 680 are tens or group relays, operated from the counting relays in the control unit or units. Relay (50 is a connect relay, companion to the relay 520 as previously mentioned. It is operated directly from relay 520 and serves to connect the remainder of the control leads to the control unit upon the seizure of the selector. The line contacts of the various tens relays of the selector are connected to local connector trunks, or to outgoing or operator trunks as required. They may also be connected to other ranks of similarly arranged selectors, in case it is desired to apply the invention to larger exchanges.

Figure 7 shows the miscellaneous control relays vfor a selector control unit. For a small exchange, one such control unit might be sufficient. It is preferable, however, in all cases, to provide a plurality of such units, each associated with a Vertical group of selectors comprising one or more selectors from each hundreds group of selectors, and in large exchanges, only one selector from any given hundreds group. Additional control units may be added jfor each vertical group of selectors as required, the control units of each group being preselected for use in rotation by a relay type allotter associated therewith. One such allotter is represented in Figure '7 by the relays 100, 105i andl "H0, relays and '|05 being the selecting relays which operate in turn to preselect an idle control unit. One of these relays is of course required for each control unit in the group. Relay 'H0 is a pull-up relay which operates theselect relays one at a time in rotation, as the control units are taken into use. Relay H is a release timing relay which operates from the exchange timer toforce the release of the switch train if dialing does not follow seizure within a given time; relay l20 is a pulsing relay which responds to the rst digit dialled over the line; relays '|25 and '|40 are release relays which operate from the pulsing relay to hold the switch train; and relay |30 is a transfer relay, which operates from release relay '|40 to prepare the pulsing ci-rcuit, and releases at the end of the rst digit to open this circuit. Relays 150 and '|60 are discriminating or service restriction relays which operate as previously mentioned from corresponding relays in the nder control equipment to identify trunk calls, and to prevent certain subscribers from making trunk calls.

In Figure 8 are shown the counting relays of the control unit partly shown in Figure 7. These counting relays operate from the pulsing relay |20 in response to the first digit, and serve in turn to operate the tens relays of the selectors in accordance with the digit dialled. These counting relays, together with relays 'H5 to 'i60 inclusive in Figure 7, constitute a first common control unit, a second similar and associated control unit being indicated byk the rectangle T84 in Figure 7.

In Figure 9, relays 900 to 025 may be considered as the group access relays, and relays 930 to 950 as the group select relays. One group access relay such as 900 or SIU is required per selector group, for each selector in the group. These relays operate when seized by the associated selector and connect the units marking leads from the selector through to the associated group select relays. are lockout relays which operate momentarily when any access relay is operated, to open the circuit of the other access relays, while relay 925 is a normally energized kickoi relay, which restores to give the busy signal and preselect the next idle trunk in case an extended call is not cut through promptly.

Similarly, one group select relay such as 930 or 900 is required per selector group, for each hundreds trunk group. These relays operate from the tens relays of the selectors and extend the units marking leads from the operated group access relay through to the proper group of trunk selectV relays, such as those of Figure 10. Relay 945 and 950 are lockout relays like e|5 and 920, which operate momen-v tarily while any group select relay is operated, to open the circuit of the other group select relays.

Figure 10 represents a group of trunk select relays equipped to handle six trunks, relays being shown however, for trunks I, 2, 5 and 6 only. In this circuit, a trunk busy relay such as |000, |005, |I)I0 or |0|5 is required for each trunk in the group. Each trunk` busy relay is normally operated through a series of break contacts in the associated connector or repeater as the case may be, and releases whenever the said connector or repeateris seized by a call. Likewise, a trunk select relay, such asV |020,

Relays SI5 and 920 |030, |040'or |050 is required for each. trunk. These relays operate one at a time rotation under the control of the trunk busy relays, to preselect the next idle trunk. As each select relay operates, it releases the preceding select relay, and prepares an operate circuit to the proper selector units relay or relays. Relay |000 is a meter relay for the control of traine meters such as peg count, all-trunks-busy and overflow meters, where required, and relay |065 is a reset relay, which operates on the seizure of the lastftrunk to reset the select relay chain. These trunk groups of course can be readily expanded, contracted, or rearranged in almost any manner, and the trunks do not have to start with the first terminal in the group, nor do they have to be assigned to consecutive terminals in thev group.

Figure 11 shows the miscellaneous relays of the connector. Relay |00 is a forced release relay,- which is operated from the common control equipment on a reverting call, to disconnect the connector line relay. It also operates from the P. B. X` trunk-selecting relays on a call to a` P. B. X having all its trunks engaged. It also serves to force the release of the connector when dialing is delayed too long, and to momentarily busy the idle connectors associated with a given control unit while said control unit is in use. Relay I |05 is a battery reversing relay operated from the back bridge relay ||I5 when a call is l answered, to reverse. the battery feed to the calling line for supervisory or metering purposes as required. Relay IIIEl is a line relay controlledy over they calling line; relay I |20 is a release relay controlled from the line relay; relay H is a hold relay controlled from the release relay tohold the preceding switches; and relay H is a switching relay operated from the controll unit when a call is answered, to switch the call through to the called line. Relay I is a trunk call relay which operates on all calls from trunks, to cut off the conversation timing. It is controlled from the service restriction relay of Figure '7. Relay IIl5 is a toll trunk call relay, which is operated from the iinder on calls from a toll Yoperator to permit verification service. Relays H50 and H60 are the verification relays, which may be operated by the toll operator, upon dialing an eXtra digit, in order to cut in on a busy line. These relays are controlled over a special pulsing lead from the control unit. Relays I and I I'I0, at the lower left, are conversation timing relays, and'relay II-'I5 is one of the connect relays, which operate upon the Seizure of the connector to connect the control leads thereof to the control unit.

In Figure 12, which shows the other half of the connector, relay |200 is the units switching re A lay, relays I2I0 and |220 are two of the units relays, and relays I230and |280l are two of the tens" relays. The units and units switching relays may be operated from the counting relays of the control unit, or from a group of P. B. X trunk-selecting relays, such as shown in Figure 16, While the tens relays are operated directly'from the counting relays of the control unit. Relay |250 is another connect relay also operated upon the seizure ofthe connector, to connect the rest of the control leads to the control unit. As many connect relays may be employed as required, and they may be connected in multiple as shown, or in tandem, as indicated for the selector circuit.

In Figure 13, are shown a portion of the mis--A cel'laL-neousv control relays of the common control 7. unit. In the embodiment of the invention illustrated, only one control unit is indicated for a given group of connectors. The connectors associated with any given control unit should preferably be taken however, from diierent hundreds groups, so that failure of a control unit will not affect an entire hundreds group of connectors.

Relay |300, in Figure 13, is a release timing relay, which is controlled from the exchange timer to prevent the control unit being held by a call beyond a certain time. Relay |305 is a counting chain release relay, which operates after each digit to release the counting relays of Figure 14. Relay |310 is a dialing transfer relay, which operates at the start of each digit received from the connector line relay, and releases at the end of each digit, to close the operating circuits through the contacts of the counting relays. Relays |3|5 to |340 inclusive are digit transfer relays, which operate successively in pairs after each digit to prepare the proper ones of the operating circuits though the counting relay contacts. Relay |350 isa permanent timing relay, which operates upon seizure of the control unit to connect the release timing relay to the timer. Relay |360 is a busy relay which operates over the connector CN lead to give busy tone to the calling line if the called line is found busy, and relay |310 is a reverting call relay which operates from the connector C lead on a reverting call, to cause the partial release of the connector when the calling party hangs up. Relay |380 is an idle test relay which operates over the connector CN lead if the called line is idle,

while relay |385 is a switching relay which operates from the idle test relay to prepare an operating circuit for the ring pickup relay |395, which then operates from the ringing interrupter to start the ringing.

In Figure 14 are shown the counting relays of the connector control unit. These relays operate from the connector line relay, and serve in turn to operate the connector tens and units relays and to select the proper ringing code, in accordance with the digits dialled into said connector.

Figure 15 shows the balance of the miscellaneous control relays of the connector control unit. Relay |500 of this figure is a coding relay, which operates from the ringing interrupter, by way of the counting relays to ring the called line; relay |5|0 is a ring reversing relay, which is also controlled from the counting relays to determine the side of the line to be rung; relay |520 is a ring cutoff relay, which operates over the called line to stop the ringing, when the called party answers; and relay |530 is a drain relay which operates from the coding relay to remove the condenser charge from the called line. Relay |540 is an additional back-bridge relay which operates over the called line if the called party answers during a silent period, to cut 01T the ring, and to switch the call through. Relay |550 is a reverting call release timing relay which operates from the timer on a reverting call, to force the release of the connector and the control unit after the called party has answered. Relays |560 to |590 inclusive are ring limiting" relays which operate from the ring pickup relay to free the common equipment after three ringing cycles.

In the P. B. X trunk-selecting relays of Figure 16, relays |600 to |630 are group access relays, relays |640 and |650 are group select relays, and relays |660 to |680 are trunk select relays. One group access relay such as |600 or |6|0 is lrequired per connector group, for each connector in the group. These relays operate when seized by the associated connector, and cut the units marking leads from the connector through to the associated group select relays. Relays |620 and |625 are lockout relays which open the operate circuits of the other group access relays momentarily when any access relay in the group operates, and relay |630 is a release forcing relay, Which falls away if an extended call is not switched through promptly, and releases the switch train.

Similarly, one group select relay such as |640 or |650 is required per connector group, for each P. B. X trunk group. These relays operate from the tens relays of the connectors and extend the units marking leads from the operated group access relay through to the proper group of trunk select relays.

Relays |660 to |680 inclusive represent a group of trunk select relays adequate for handling ve trunks, one such relay being required for each trunk. They are normal when the associated trunks are idle, and operate one at a time as the corresponding trunks become engaged. The function of each of these relays is to prepare an operate circuit to the corresponding connector units relay, which circuit is completed upon the dialing of the P. B. X call number to select an idle trunk. Trunk rotation is not provided, and the rst idle trunk is chosen in al1 cases. If more than five trunks are included in the group, the units switching relay of the connector will be operated, as well as the proper units relay, for calls directed to any trunk beyond the fifth. The break contacts of the last trunk select relay are strapped so that when all trunks are busy, all further calls will be directed to the last trunk, in order to operate the busy circuits.

Figure 17 shows in schematic form, two selectors of a group, and two common control units associated therewith, in order to show the manner in which the control circuits are multipled between the connect relays, the selectors, and the control units. The two selectors are represented by the dotted rectangles |160 and |185, and the two control units by the small rectangles directly below, numbered |190 and |195. In selector |180, the relays 500 and 5|0 are the switching and busy relays of Figure 5, and relays 520 and 650 are the connect relays of Figures 5 and 6, serving the iirst common control unit |190. Relays and |1 I0 in this selector, are similar connect relays serving the second common control unit In the second selector |185, relays and are again the switching and busy relays, relays and |150 are the connect relays serving the rst common control unit and relays and |110 are the connect relays serving the second common control unit. The other selectors of the group would be connected in an identical manner, it being understood that each pair of control leads such as |1 I5 and |1|6, shown passing through make contacts on each connect relay of Figure 1'7, represent all of the multipled control leads shown in connection with relays 520 and 650 of Figures 5 and 6 not otherwise indicated in Figure 17. To provide an additional control unit for the same group of selectors, would require, in addition to the extra control unit, another pair of connect relays in each selector, and an additional select relay such as 105, in the control unit allotter, inserted between the relay 105 and the reset relay 1 |0. 

